Obesity is the cause of many adverse pregnancy outcomes and as a result, has a great impact on the health of women and their children. It is hypothesized that during pregnancy obese women will have increased HbA1c, decreased vagal response and oxygenation compared to non-obese women. Forty pregnant women of four major ethnic groups will be observed three times for 30 minutes at 20, 28, and 36 weeks gestation, 20 each with obese and non-obese status determined by their body mass index. The time points for observation have been selected because after 20 weeks the fetus could be viable if born; at 28 weeks the fetus if born would be preterm and at this stage, maternal disorders such as hypertension or diabetes may become clinically apparent with the stress of pregnancy and gestational weight gain; and at 36 weeks the fetus will be close to term birth. Pregnancy complications and infant outcomes will be followed by chart audits and interviews of subjects. The tentative analysis plan will include descriptive statistics, t-tests for two group comparisons, and, repeated measures ANOVA to test the group differences with changes over time. Correlations and regression analyses will be performed to examine the association of obesity and levels of gestational weight gain on vagal response, HbA1c, oxygenation, and pregnancy complications and birth outcomes. For an effect size of 1, 17subjects will be needed to detect a difference with a power of 80%. Considering a 20% attrition rate [as may occur with preterm birth, 20 women per group is proposed.